1. Field of the Invention
This invention relates to a floating shoe shuffling tunnel boring machine having orthogonal anchoring shoe pairs floating relative to the machine body and cutterhead which shoe pairs are set against the tunnel wall in alternating sequence.
Many types of tunnel boring machines have been patented and/or produced which are generally characterized by having a cutterhead carried by and rotatable relative to the machine body to pulverize or comminute rock at the face of a tunnel. The muck is conveyed longitudinally through the boring machine for removal from the tunnel. Representative examples of patents on tunnel boring machines are discussed below.
2. The Problem
Tunnel boring machines are expensive so that it is desirable to provide a tunnel boring machine which will accomplish the tunnel boring operation as quickly as possible. The boring speed can be increased if the cutterhead is advanced continuously against the tunnel face at maximum cutting speed. The cutting speed will be limited by the effectiveness of the cutting operation of the cutterhead and by the material of the tunnel face which is being cut, but whatever the limitation may be on the cutting speed, operating the cutterhead so that it will be cutting continuously will greatly reduce the tunneling time required over the time spent by utilization of a boring machine the cutterhead of which cuts intermittently.
3. Prior Art
The Robbins et al. U.S. Pat. No. 3,203,737, issued Aug. 31, 1965, states at column 4, beginning at line 1:
Now proceeding to describe said gripper shoes, which function to support the machine during boring operations and are designated by 27, the same are opposingly mounted one at each of the two sides of the machine adjacent the mid-length of the latter. Extending laterally of the machine between these two shoes is the gripper mounting assembly, generally designated by 28. This assembly comprises three basic parts, namely, two open-center cross-heads 30, each of which carries a respective one of the two gripper shoes 27, and a muff 31 producing slideways in each of its two ends for a respective one of the two cross-heads. This mounting assembly has two significant functioning characteristics: (1) the cross-heads can be forced outwardly from one another within the muff by pressure exerted from a set of four large hydraulic gripper jacks 32, which responsively presses the gripper shoes 27 firmly against the tunnel side wall, and (2), with the gripper shoes thus firmly planted, the muff 31 can be shifted laterally, sliding on such localized cross-heads, by means of a set of two smaller hydraulic steering jacks 33. This lateral shifting provides transverse steering for the machine. PA1 When the gripper shoes 27 are in retracted position (i.e. withdrawn from the side wall of the tunnel), the machine is supported by the three steering shoes 20-21-21 at the front of the machine, and by the rear foot 26. To move the gripper shoes 27 forwardly to a gripping position from which the machine can be advanced, and assuming that said shoes have been retracted from the wall, the four thrust jacks 37 are retracted so as to draw the gripper mounting assembly 28 and the carriage 34 forward on the machine frame. The slide mounting therefor is provided by the jumbo bars 36A and 36B. When the gripper shoes 27 have reached their forward limit of travel, the gripper jacks are extended to plant the gripper shoes firmly against the two lateral surfaces of the tunnel side wall. PA1 When the machine frame has been properly located and it is desired to then proceed with the boring of the tunnel, straight-line boring is performed by extending the four thrust jacks 37 at equal rates, the thrust jacks pushing against the anchored gripper shoes 27 and responsively forcing the cutting head forwardly in the tunnel. PA1 The front shoes 20-21-21 co-operate with the gripper shoes 27 in supporting the machine. While the machine is performing its boring function, these shoes 20-21-21 have only sliding contact with the tunnel wall, bearing against the wall only in the degree necessary to stabilize the rotary head. PA1 The wall-engaging outer faces of the anchoring shoes 42 are generally rectangular in plan configuration, and have projecting spikes 43 for augmenting the wall purchase. When viewed from an end said outer faces are convex to conform to the curvature of the tunnel wall . . . PA1 When the anchor shoes 42 have been retracted from the tunnel wall incident, say, to moving the shoes forward for taking a grip at a new location, the machine is supported by the front-end guide shoes 34 and by a rear foot 100. This rear foot is operated by a hydraulic jack and during working periods of the machine is kept retracted. For said forward movement of the shoes (the present machine being engineered for a 2-foot stroke) the four thrust jacks 81 are retracted. This draws the disengaged shoes ahead, causing the steering box to slide upon the trunk in concert with such advance. Upon reaching the forward limit of this resetting "step," the operator charges pressure fluid into the cylinders 57 of the carriage 41, forcing the pistons outwardly within said cylinders to cause the anchor shoes to be again firmly planted against the tunnel wall. PA1 All thrust forces are passed through the jacks 81 from the main body directly to the anchor shoes. With this machine also, a boring operation can be accomplished only when the anchor shoes 42 are planted against the tunnel wall so that the boring operation must be interrupted while the anchor shoes are retracted from the tunnel wall and are being moved forward for gripping the tunnel wall at a new location, as described in the portion of the Winberg et al. patent quoted above. PA1 The mechanism which advances the boring machine forwardly in the tunnel includes a gripper assembly which is basically like the gripper assembly disclosed by the aforementioned U.S. Pat. No. 3,203,737. PA1 The gripper assembly 30 may comprise a gripper carrier 32 having a transverse passageway 34 formed therein in which two collinear gripper cylinders 36, 38 are housed. The cylinders 36, 38 comprise piston chambers which are rigidly connected together at their closed ends by upper and lower beam members 40, 42. A piston, one of which is designated 44, is located within each cylinder 36, 38. Piston rods 46, 48 extend outwardly from the pistons (44) and at their outer ends are connected to tunnel wall engaging gripper pads 50, 52. Note that there are only two cylinders 36 and 38 actuating only two piston rods 46 and 48, respectively. PA1 Forward feeding of the cutterhead is accomplished by thrust rams or cylinders 72, 74 inclined forwardly from the gripper shoes 50 and 52, as shown in FIGS. 1, 7, 8 and 9 and described in column 3, beginning at line 23: PA1 In the conventional manner, a pair of double-acting hydraulic thrust rams or cylinders 72, 74 are interconnected between the gripper pads 50, 52 of the gripper assembly 30 and forward portions of the frame 12, in the vicinity of the cutterhead support 14. PA1 FIG. 1 shows the boring machine at the start of an advance. The gripper cylinders 36, 38 are extended, forcing the gripper pads 50, 52 outwardly into gripping contact with opposite side wall portions of the tunnel. Hydraulic fluid is delivered into the thrust rams 72, 74 to cause their extension. As they extend they react rearwardly against the gripper assembly 30 and shove the frame 12, and the cutterhead 18 carried thereby, axially forwardly against the tunnel face. At the same time the motors 20 are operated to rotate the cutterhead 18. Cutterhead rotation and machine advance causes the disc cutter elements 26 to cut concentric kerfs in the tunnel face and to dislodge the material between the kerfs. The dislodged material is picked up by the scoops 28 and delivered into an overhead chute which deposits such material onto the conveyor housed within the beam 16. As the frame 12 moves forwardly the guide rail 62 moves forwardly through the guide bearings 58, 60 on the carrier 32. When the propulsion rams 72, 74 reach the ends of their stroke, the cylinders 36, 38 are retracted to withdraw the gripper pads 50, 52 from engagement with the tunnel wall. Then, the propulsion rams 72, 74 are retracted to in that manner pull the gripper assembly 70 forwardly along the rail 62. When the gripper assembly is at a forward position on the rail 62, the cylinders 36, 38 are again extended and the above described procedure is repeated. PA1 These cylinders react rearwardly against the gripper assembly and when they are extended serve to push the frame and the cutterhead carried thereby forwardly in the tunnel. At the end of the stroke the gripper assembly is retracted from the tunnel wall and is pulled forwardly by the cylinders into a new position. It is then extended laterally to take a new grip on the tunnel wall and the process is repeated. PA1 The gripper shoes 18 are extended to grip the tunnel wall to in that manner anchor the rear shield 12 in place in the tunnel. The forward thrust rams 52 are extended for the purpose of shoving the front shield 10 forwardly relative to the anchored rear shield 12. The cutterhead 60 is rotated to mine the tunnel face 70 as the shield 10 is being moved forwardly. Following full extension of the thrust rams 52 the gripper feet 18 are retracted and the thrust rams 52 are used for pulling the rear shield forwardly relative to the front shield 10. After the thrust rams 52 are fully retracted, and the rear shield 12 is in its new position forwardly of its old position, the gripper feet 18 are again extended and the above described operation is repeated. PA1 The thrust cylinders 52 are used for pushing the front shield 10 forwardly relative to the anchored rear shield 12 while the cutterhead 60 is driven for the purpose of mining the tunnel face 70. Following full advancement of the forward shield 10 the gripper feet 18 are retracted and the thrust cylinders 52 are used for pulling the rear shield 12 forwardly into a new position. The rear thrust rams 48 may have to be used to aid forward movement of shield 12. In other words, the rear thrust rams 48 may be extended rearwardly to react against the forward segments S of the tunnel lining TL. Following extension of the thrust rams 48 the gripper feet 18 are again extended for the purpose of anchoring the rear shield 12 in place of the tunnel. Then, the front shield 10 is again pushed forwardly relative to the rear shield 12 by use of the thrust rams 52. PA1 The pads 112 may also be extended for the purpose of gripping the tunnel wall for the purpose of helping to anchor the forward shield 10 in place while the rear shield 12 is being advanced forwardly. PA1 During tunneling the rear shield 12 is anchored in place by virtue of the fact that the gripper feet 18, 19 are extended outwardly into gripping contact with the tunnel wall. PA1 Referring to FIGS. 1 and 6-8, an advancement sequence of the machine will now be described. Let it be assumed that the machine is initially in the position shown by FIG. 1. The auxiliary thrust rams 48 are reacting against the forward end portion of the tunnel lining TL and the main thrust rams 52 are being operated for moving the forward shield 10 forwardly relative to the rear shield 12. PA1 Following full extension of the main thrust rams 52, such main thrust rams are retracted and the rear shield 12 is advanced an amount equal to the stroke of the main thrust rams 52. PA1 Following forward movement of the rear shield 12 the main thrust rams 52 may again be extended for the purpose of further advancing the front shield 10. PA1 The gripper shoes 18 are extended to grip the tunnel wall to in that manner anchor the rear shield 12 in place in the tunnel. The forward thrust rams 52 are extended for the purpose of shoving the front shield 10 forwardly relative to the anchored rear shield 12. The cutterhead 60 is rotated to mine the tunnel face 70 as the shield 10 is being moved forwardly. Following full extension of the thrust rams 52 the gripper feet 18 are retracted and the thrust rams 52 are used for pulling the rear shield forwardly relative to the front shield 10. After the thrust rams 52 are fully retracted, and the rear shield 12 is in its new position forwardly of its old position, the gripper feet 18 are again extended and the above described operation is repeated. PA1 The thrust cylinders 52 are used for pushing the front shield 10 forwardly relative to the anchored rear shield 12 while the cutterhead 60 is driven for the purpose of mining the tunnel face 70. Following full advancement of the forward shield 10 the gripper feet 18 are retracted and the thrust cylinders 52 are used for pulling the rear shield 12 forwardly into a new position . . . Following extension of the thrust rams 48 the gripper feet 128 are again extended for the purpose of anchoring the rear shield 12 in place in the tunnel. Then, the front shield 10 is again pushed forwardly relative to the rear shield 12 by use of the thrust rams 52. PA1 . . forward advancement of the shield 12 is achieved by use of thrust rams 48 alone. Also, the tunnel lining is erected while the machine is stopped, following extension of rams 48 to move shield 12 forwardly and then retraction of the rams 48 to provide spaces for receiving new segments of the lining. PA1 Frame 84 also includes a pair of generally radial guideways 90 for a pair of side positioned, diametrically opposed gripper shoes 92, 93. The shoes 92, 93 are extended and retracted by a pair of upper and lower double-acting hydraulic cylinders 94, 96. The upper cylinder 94 is interconnected between mounting ears 98, 100 at the upper ends of the gripper shoes 92, 93. In similar fashion, the lower fluid cylinder 96 is interconnected between mounting ears 102, 104 at the lower ends of the shoes 92, 93. PA1 The prior art includes the double shield tunnel boring machine disclosed in Robbins et al U.S. Pat. No. 4,420,188. The novel improvement in the present invention over that shown in the Robbins et al patent involves the use of a series of at least three pairs of hydraulic primary propel cylinders between the first and second shields, with each pair of primary propel cylinders being arranged in a V-shaped configuration having an included angle of about 15.degree. to 60.degree. in a plane generally parallel to the adjacent portions of the shields and with the line bisecting the included angle being substantially parallel to the longitudinal centerline of the machine. The pairs of primary propel cylinders rigidly tie the first and second shields together and perform the multiple functions of axial thrust (by simultaneous actuation), of transmitting reaction torque from the cutterhead support to the gripper system thereby countering the reverse rotary displacement of the cutterhead support caused by the rotary torque applied to the cutterhead, of steering (by selective actuation causing angular displacement of the first shield, the cutterhead support, and the cutterhead relative to the second shield which is held stationary by the gripper system), and of roll correction (by selective actuation causing clockwise or counterclockwise rotation of the first shield, the cutterhead support, and the cutterhead relative to the second shield which is held stationary by the gripper system). Thus, the novel primary propel cylinder pairs have a forward thrust function, a reaction torque function, a steering function, and a roll correction function. They provide at all times a rigid structure between the first and second shields, replacing the conventional axially disposed rearwardly extendable thrust cylinders (such as the thrust rams 52 in Robbins et al. U.S. Pat. No. 4,420,188), eliminating the need for separate reaction torque cylinders (such as the reaction torque cylinders 152 and 154 in the Robbins et al. patent), and also eliminating the need for precise control of the length of the reaction torque cylinders during the axial thrust stroke (such as in the Robbins et al. patent where, in order to maintain the first shield nonrotative with respect to the second shield, the extension of the torque cylinders 152 and 154 had to progressively change during the pivotal movement thereof caused by the forward axial movement of the first shield). PA1 . . controlling the pairs of primary propel cylinders to effect (1) axial forward thrust on the cutterhead by simultaneous actuation of all the primary propel cylinders . . . PA1 As a second step, while rotating the cutterhead about its substantially horizontal axis, axially thrusting the cutterhead forward into the rock work face by simultaneously actuating all of the primary propel cylinders located rearwardly from the cutterhead . . . PA1 The rear shield assembly 14 telescopes into the front shield 12. In this respect, the present invention is similar to the machine disclosed in Robbins et al. U.S. Pat. No. 4,420,188, the disclosure of which is incorporated herein by reference. The front shield 12 comprises a rear section 16 which overlaps the forward portion 18 of rear shield 14. PA1 The cutterhead support 32 (FIG. 3) and the front shield 12 support the cutterhead 25 . . . The front shield 12 forms the outer structure of the cutterhead support 32. PA1 The front shield 12 also houses the front stabilizer shoes 33 which extend during the boring operation to stabilize the cutterhead 24 and to lock the front shield 12 in the tunnel so that the rear shield 14 can be pulled forward during the recycle. PA1 The large area crab leg, window type gripper system 35 mounted on the circular rear shield/gripper support frame 23 provides low unit ground loading for reacting machine thrust, torque, and steering forces. PA1 The telescoping rear shield 14 consists of the shield structure, the crab leg window-type gripper system 35, a forward shield section 18 which telescopes into the front shield 18 which telescopes into the front shield 12, a tail section 20, and eight auxiliary thrust cylinders 38 (FIG. 4). PA1 The three gripper shoes 57, 59, and 61 (FIG. 4) operate through windows in the rear shield 14. The right and left gripper shoes 59 and 61 are hinged on pins 63 and 65 in mounting brackets 78 and 80 which are secured to the lower portion of the rear shield/gripper support frame 23. PA1 The angled primary propel cylinders 28 are double acting hydraulic cylinders and are mounted in pairs between the front shield 12 and the rear shield 14. The propel cylinders 28 are mounted on the trunnion-type front mounting brackets 13 secured to the cutterhead support 32 and on the trunnion-type rear mounting brackets 15 secured to the rear shield/gripper support frame 23. PA1 As shown in FIGS. 1 and 3, the primary propel cylinders 28 are arranged annularly in four equally spaced pairs located between the front shield 12 and the rear shield 14. PA1 The pairs of propel cylinders 28 rigidly tie the first and second shields 12 and 14 together. Furthermore, the propel cylinders 28 perform the multiple functions of axial forward thrust when the propel cylinders 28 are all simultaneously actuated . . . PA1 The primary propel cylinders 28 (FIG. 3) are anchored to the front shield 12 and thrust against the rear shield/gripper support frame 23 into the gripper shoes 57, 59, and 61 into the tunnel wall. PA1 The operating cycle of the tunnel boring machine 10 is next described. The machine 10 advances with an stroke of about 1.2 meters. This advance is provided by extension of the primary propel cylinders 28. Primary thrust reaction is provided by the gripper shoes 57, 59, and 61 which are expanded to contact the tunnel walls by the gripper cylinders 30 and 36 . . . PA1 The cutterhead 24 then excavates about 1.2 meters of heading. When the advance is completed, the gripper shoes 57, 59, and 61 are retracted by retracting gripper cylinders 30 and 36. The rear shield assembly 14 is then moved forward by retraction of the primary propel cylinders 28 and extension of the rear auxiliary thrust cylinders 38 and the cycle i [s] then repeated. It is therefore evident that the machine disclosed in this patent also performs an intermittent boring operation. PA1 The basic parts of the tunneling machine are a main frame which includes a cutterhead support 10 attached to a tubular shield 12 and a rearwardly projecting beam 14. A gripper assembly 16 is supported for relative sliding movement along a straight portion of the beam 14. Thrust rams 18, located on both sides of the machine, are interconnected between the cutterhead support 10 and the gripper assembly 16, generally in the manner disclosed by U.S. Pat. No. 3,203,737, granted Aug. 31, 1965 to Richard J. Robbins, Douglas F. Winberg and John Galgoczy, and by U.S. Pat. No. 3,861,748, granted Jan. 21, 1975, to David T. Cass. PA1 As is well known in the tunneling machine art, the gripper assembly 16 is positioned forwardly on the beam 14. Its gripper shoes 17 are hydraulically moved outwardly into gripping contact with the side walls of the tunnel. Then, the thrust rams 18 are extended while the rotary cutterhead is being rotated by means of a plurality of drive motors 22. . . When the cylinders 18 reach the forward limits of travel the gripper pads 17 are retracted and the cylinders 18 are retracted for the purpose of drawing the gripper assembly forward into a new position. Then, the gripper pads 17 are again moved outwardly into contact with the tunnel wall and the boring procedure is repeated.
The description continues at column 4, line 60:
After the shoes are thus reset, the interrupted boring operation then continues as stated at column 5, beginning at line 24:
The resistance to the boring operation is effected only by the gripper shoes 27, as stated at column 5, beginning at line 42:
This machine, therefore, has an intermittent boring operation performed only while the gripper shoes 27 are set against the tunnel wall.
The later Winberg et al. U.S. Pat. No. 3,295,892, issued Jan. 3, 1967, discusses the Robbins et al. U.S. Pat. No. 3,203,737 at column 1, lines 28 to 45. The Winberg et al. patent machine is stated to have been designed for tunnels of say seven feet diameter, whereas the machine of the above Robbins et al. patent is stated to have been designed to bore quite large tunnels, for example sixteen feet in diameter. The Winberg et al. patent, like the Robbins et al. patent, is assigned to James S. Robbins and Associates, Inc.
Diametrically opposite anchoring shoes 42 of the Winberg et al. patent shown in FIGS. 3 and 4 are described at column 3, beginning at line 11:
The muck cut from the tunnel face is removed by the endless conveyor 26 shown in FIG. 1 as being inclined upward over the jack mechanism projecting the anchor shoes 42 oppositely, as described in column 2, lines 32 to 39.
The boring operation is described beginning at column 5, line 28, as follows:
The description continues at column 5, line 74:
Cass U.S. Pat. No. 3,861,748, issued Jan. 21, 1975, refers to the Robbins et al. U.S. Pat. No. 3,203,737 discussed above at column 1, lines 13 to 15, and states in column 2, beginning at line 47:
The description then continues at column 2, line 51:
The operation of the machine is described at column 3, beginning at line 28:
It is evident that the cutterhead is not being moved forward when the cylinders 36 and 38 are retracted to withdraw the gripper pads 50, 52 from engagement with the tunnel wall and the propulsion rams 72, 74 are being retracted to pull the gripper assembly 70 forward to place the gripper pads 50, 52 at a new location. Again, therefore, the digging operation of this tunnel-boring machine is intermittent.
The title of Grandori U.S. Pat. No. 3,967,463, issued Jul. 6, 1976, is CONTINUOUS TUNNEL BORING MACHINE AND METHOD. This patent discusses the Robbins et al. U.S. Pat. No. 3,203,737 referred to above at column 1, lines 22 to 39, the portion from column 1, line 32 to line 39 stating:
The operation of the Grandori machine is described at column 5, beginning at line 5, as follows:
Note that, after the thrust rams 52 are fully extended, the gripper feet are retracted and the thrust rams pull the rear shield forward. During that operation, it is evident that the boring procedure is interrupted so that the boring action of the machine is intermittent rather than being continuous.
The description continues at columns 5, line 25:
Thus, it is clear that the cutting operation of the Grandori machine is intermittent.
In the machine of the Grandori patent, as in the machine of the Cass patent, there are only two gripper shoe or feet operating jacks 80 and 82, as stated at column 5, lines 50 to 52. As stated above, with reference to lines 9 to 11 of column 5, the cutterhead mines the tunnel face as the front shield 10 moves forward, but when the gripper shoes or feet are being moved forward for resetting the front shield 10 remains stationary so that the tunnel face is not being mined. As stated at column 6, beginning at line 42:
The operation is further explained in column 7, beginning at line 16:
The operation is further described beginning at column 7, line 59:
Continuing at column 8, line 3:
While the rear shield is being advanced by contraction of the rams 52, the front shield and the cutterhead being carried by it will remain stationary. The description then continues at column 8, line 11:
The double shield tunnel boring machine disclosed in Robbins et al. U.S. Pat. No. 4,420,188, issued Dec. 13, 1983, has aspects similar in appearance to the machine shown in Grandori U.S. Pat. No. 3,967,463. Compare, for example, FIGS. 1, 2, 3 and 4, of the Grandori patent with FIGS. 3, 4, 5 and 6 of Robbins et al. Pat. No. 4,420,188, respectively. Both of these patents are assigned to The Robbins Company, and application Ser. No. 481,292 filed Jun. 20, 1974, is mentioned in the Robbins et al. Pat. No. 4,420,188 at column 1, lines 11 and 12, and application Ser. No. 481,393, filed Jun. 20, 1974, is mentioned in the Grandori patent at column 1, lines 9 to 11. Robbins et al. Pat. No. 4,420,188 issued on the basis of a continuation-in-part application of Ser. No. 802,878, which was a continuation of Ser. No. 677,709, which was a continuation of Ser. No. 481,292, or perhaps Ser. No. 481,393.
Also, Robbins et al. Pat. No. 4,420,188 refers to the earlier Robbins et al. Pat. No. 3,203,737 discussed above at column 1, lines 24 to 41.
The machine of the Robbins et al. Pat. No. 4,420,188, like that of the Grandori patent, has a front shield 10 and an anchored rear shield 12, as shown in FIG. 1 and described in column 5, beginning at line 5:
This statement is identical with the description in Grandori Pat. No. 3,967,463 at column 5, beginning at line 5. Again, therefore, it is evident that the cutterhead 10 is not being rotated to mine the tunnel face while the front shield 10 remains stationary and the rams 62 are being used for pulling the rear shield forwardly relative to the front shield 10 rather than the front shield being moved forward relative to the anchored rear shield. As in the other patents discussed, the machine of this patent performs an intermittent cutting operation. Such operation is further described in column 5, beginning at line 25:
The statement in this patent from column 4, line 27, to column 5, line 48, is the same as that in Grandori Pat. No. 3,967,463 from column 4, line 27, to column 5, line 49.
That the machine of the Robbins et al. Pat. No. 4,420,188 is stopped at times is further stated at column 5, beginning at line 47:
The gripper shoes are set by only one pair of hydraulic cylinders 94, 96, as stated beginning at column 5, line 65:
The later Turner U.S. Pat. No. 4,548,443, issued Oct. 22, 1985, and also assigned to The Robbins Company, refers to the earlier Robbins et al. U.S. Pat. No. 4,420,188, discussed above, at column 1, line 27 to column 2, line 3. In this patent the shield 12 is the front shield (column 3, lines 40,41, 44, 45, 52 and 54, and column 4, lines 17, 23, 31, 40, 50, 56 and 62), whereas the rear shield is designated 14 (column 3, lines 40, 41, 46 and 52, and column 4, lines 20, 24, 32, 41, 52 and 57). The general arrangement and operation of the machine in Pat. No. 4,548,443 is, however, similar to the machine of U.S. Pat. No. 4,420,188 and U.S. Pat. No. 3,967,463. The principal difference is explained in column 1, beginning at line 27:
The boring operation effected by the machine of Pat. No. 4,548,443 is an intermittent operation as discussed in connection with the other patents. Advance of the cutterhead is accomplished by joint action of all of the propel cylinders, as stated at column 2, beginning at line 28:
and further beginning at line 44:
With respect to the front and rear shields, it is stated at column 3, line 40 that:
The front shield 12 supports the cutterhead, as stated at column 4, line 11:
That the cutting operation of the machine of U.S. Pat. No. 4,548,443 is intermittent is indicated by the statement at column 4, beginning at line 17, that:
Since the front shield 12 is locked to the tunnel while the rear shield 14 is pulled forward, the cutting operation cannot continue because it is dependent on the front shield 12 being moved forward during the cutting operation.
The rear shield 14 is described beginning at column 3, line 57, as follows:
The rear shield is further described in column 5, beginning at line 14 as follows:
Since the rear shield 14 is a continuous annular structure in which the windows are formed, the gripper shoes 57, 59 and 61 can have no relative movement longitudinally of the machine.
The angled propel cylinders are connected to the support frame 23 which is a rigid part of the rear shield 14 and are not connected directly to the gripper shoes 57, 59 and 61, as stated at column 4, beginning at line 21:
The description continues at column 4, line 39:
The propel cylinder arrangement is further described beginning at column 5, line 27:
Again, it is clear that the propel cylinders do not engage directly and are not connected directly to the gripper shoes 57, 59 and 61 but are connected to the support frame 23 which controls the position of the gripper shoes operating in windows in the rear shield, as stated above.
The operation of the machine is described in column 5, beginning at line 33:
Spencer U.S. Pat. No. Re. 31,511, reissued Jan. 31, 1984, and also assigned to The Robbins Company, discusses its advancing mechanism beginning at column 3, line 67:
The machine of this patent also executes an intermittent boring operation which is interrupted while the gripper assembly carrying the gripper shoes or pads 17 is moved forward relative to the cutterhead into a new position.
A tunneling machine for which no patent application was filed was operated at Stillwater, MN., by Traylor Brothers, Inc., during the years 1981 and 1982. This machine had a central body rigidly connected to a support for a rotary boring head, the central portion of which body was hollow. A conveyor passed longitudinally of the machine through the body hollow for conveying muck from immediately behind the cutterhead to the rear of the machine. The body and cutterhead were advanced by longitudinally extending advancing jacks connected between the body and a set of anchor shoes arranged circumferentially around the hollow body. There were twelve of such shoes and twelve advancing jacks. The shoes were individually pressed against the tunnel wall by short, radially disposed, anchor-setting jacks pivotally connected both to the body and to the respective shoes. Reaction thrust was exerted on the body by rocking bases for the respective jacks bearing on the body as the cutterhead, body and jack bases were advanced relative to the anchor shoes.
With this construction, the setting cylinders of alternate shoes could be extended to set the shoes corresponding respectively to those jacks constituting a first set of shoes, whereas the setting jacks for the other alternate shoes, constituting a second set, would be sufficiently retracted to enable the jacks of such second set to slide along the tunnel wall. The advancing jacks connected between the shoes of the first set and the body of the machine would be extending to advance the machine body and cutterhead while the set of advancing jacks corresponding to the other set of anchor shoes would be contracting to slide the other set of anchoring shoes forward. Because the body was being moved forward relative to the unanchored set of anchor shoes, the setting jacks for the shoes of such set would be moving into forwardly and outwardly inclined positions relative to the forwardly moving body.
The difficulty with the Stillwater machine was the complexity of the apparatus caused by the large number of anchor shoes and advancing jacks and the fact that the rocking bearing of the bases of the shoe-setting jacks on the tubular machine body would cause localized stress pressures on the bases of such jacks. Also, because the setting jacks for gripping sets of shoes were required to be rocked relative to the body while the body was moving forward, the forward stroke for any shoe setting was quite short.